Low temperature oxidation of novel high-performance fuels on Pt and Pd catalysts
Fan Lin, Pacific Northwest National Laboratory
Low temperature oxidation of novel high-performance fuels on Pt and Pd catalysts
Fan. Lin1, Kenneth G. Rappe1, Yong Wang*,1,2
1 Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
2 The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
To reduce petroleum consumption, the U.S. Department of Energy (DOE) “Co-optimization of Fuels and Engines” aims to simultaneously develop novel high-performance fuels and advanced high efficiency engines. Co-Optima researchers have identified a number of potential fuel blendstocks, including hydrocarbons and oxygenates, that could provide the desired changes in fuel properties. New fuel components may bring new challenges for the exhaust aftertreatment catalysts, which have been designed and optimized to deal with the conventional fuel components presented in exhausts. Majumdar et al.[1] have reported the reactivities of various components of novel high-performance fuels on a commercial three-way catalyst system consisting of Pd and Rh. However, a systematic investigation on the reactivities of fuel components on single metal catalysts (e.g., Pt, Pd, Rh) is also needed for the purpose of catalyst development to meet the aftertreatment requirement of the novel fuels.
In this work, we investigated the activities of CeO2-supported Pt and Pd catalysts for low temperature oxidation of representative components of novel high-performance fuels. First, the catalytic performance of single-atom (SA) and nano-particle (NP) catalysts were compared. The SA and NP catalysts were prepared by incipient wetness impregnation of metal precursors on CeO2 support and calcination in flowing air at 800 °C for 12h (for SA) and 500 °C for 4h (for NP), respectively, followed by reduction in 10% CO at 150 °C for 1h. The received SA samples contained a mixture of atomically dispersed metals and metal nano-clusters on the surface, whereas on NP samples are predominantly metal nano-clusters. The activities fuel oxidation on the catalysts were tested with simplified feed mixtures of O2 (0.75%) + fuel component (isooctane, isobutanol, furan, and cyclopentanone, equivalent to 3000 ppm C1). The results showed that, for both Pt and Pd catalysts and all fuel components, the NP samples were more active than SA samples with the same metal loading, with T50 lower by 15-30 °C. The CO-TPR showed that the active surface oxygen species on SA were more reducible than those on NP. These results suggested that the oxidation of fuel components on Pt and Pd catalysts were not limited by O2 activation. Instead, it was controlled by the activation of C-H or C-C bond of fuel molecules, which occurred on Pt or Pd clusters containing adjacent metallic sites. As a result, the NP catalysts which had more metallic Pt or Pd sites were more active for the oxidation of fuel components.
The activities of fuel component are affected by their functional groups. We found that Pt and Pd had different preferences for the fuel components. On Pt/CeO2-NP, hydrocarbon (e.g., isooctane) was more active than oxygenates (e.g., isobutanol, furan, and cyclopentanone), whereas on Pd/CeO2 the trend is reversed, with oxygenates being more active. This matrix of catalyst/fuel properties and reactivities is important information to guide the development of novel catalysts to deal with the aftertreatment issue of the novel-high performance fuels.
Reference:
[1] S. Sinha Majumdar, J.A. Pihl, T.J. Toops, Reactivity of novel high-performance fuels on commercial three-way catalysts for control of emissions from spark-ignition engines, Applied Energy, 255 (2019) 113640.
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